For many people, sorting their electronic mail (email) is a major part of their work and home tasks. This is particularly problematic when one goes on holiday or goes to a customer site for a day or two as one is faced with a very long list of emails and one has to prioritize their processing. Rules that help with putting received emails into known folders (or deleting them) are well known: For example, If the sender is X—move to folder Y, if my spam filter thinks it may be spam—move to junk mailbox, etc. Most such rules are created by the user.
People tend to open email in a particular order: spouse first, then boss, then colleagues, then friends, then work tasks, then local management news, then company news, then unrecognized, then delete the junk. However, doing this easily when the in-basket is large is more difficult as one has to make repeated scans through the in-basket to pick out the most important emails still not handled. If one leaves messages in the in-box long term and does not necessarily open 100% of emails, this scrolling through a long list makes ‘missing’ an email or responding slowly more likely.